Microporous Tectosilicate and Method for the Production Thereof

ABSTRACT

The present invention relates to a tectosilicate having an X-ray diffraction pattern in which at least the following reflections occur:  
                                           Intensity (%)   Diffraction angle 2θ/° [Cu K(alpha 1)]                   100    9.8-10.2         24-34   11.0-11.4          9-19   15.5-15.9         12-22   19.4-19.6         19-29   19.6-19.8                                    
100% relating to the intensity of the maximum peak in the X-ray diffraction pattern.

The present invention relates to a process for the preparation ofsilicates, in particular for the preparation of tectosilicates having azeolite structure. The present invention also relates to the silicatesobtainable by this process, in particular layered silicates andtectosilicates. The present invention furthermore relates to thesesilicates per se and the use thereof, in particular the use thereof asmolecular sieves for separating and/or isolating mixtures, in particularfor separating alkane and/or alkene gas mixtures.

In chemical production or purification processes, the object ofseparating off at least one substance from a mixture or quite generallyof separating mixtures frequently arises. In principle, this separationcan be performed by distillative methods. However, particularly in thecase of mixtures having a very narrow boiling range, these distillativemethods cannot be carried out economically or can be carried outeconomically only with the use of auxiliary agents. An example of theseparation of mixtures having a narrow boiling range is the separationof alkanes or alkenes, for example the separation of isomeric alkanes oralkenes.

It is an object of the present invention to provide compounds which canbe used as molecular sieves and/or adsorbents for such isolations and/orseparations.

It is a further object of the present invention to provide a process forthe preparation of these compounds.

It is a further object of the present invention to provide novelsilicates, in particular zeolites, which can advantageously be usedfirstly for the applications described above but also for any otherconceivable purpose, for example as catalysts or in other technicalareas.

Therefore, the present invention relates to a process for thepreparation of a silicate containing at least silicon and oxygen,comprising

-   -   (1) mixing of silica and/or of a silica precursor with an        aqueous solution comprising at least one R₁R₂R₃R₄N⁺-comprising        tetraalkylammonium compound and at least one base;    -   (2) heating of the colloidal solution obtained according to (1)        to a temperature in the range of from greater than the boiling        point of the colloidal solution under the chosen pressure to        180° C. at atmospheric pressure to give a suspension containing        at least one silicate,        wherein R₁, R₂, R₃ and R₄, independently of one another, are        selected from the group consisting of methyl, ethyl, n-propyl        and isopropyl, preferably of methyl, ethyl and n-propyl, wherein        at least two of the residues R₁, R₂, R₃ and R₄ are different        from one another.

Preferably used R₁R₂R₃R₄N⁺-comprising tetraalkylammonium compounds arecompounds in which at least one residue is methyl. Compounds in whichtwo or three residues are methyl are more preferred, and compounds inwhich two residues are methyl are particularly preferred.

According to a further, preferred embodiment, two residues are methylwhile the other two residues are ethyl or n-propyl or isopropyl.According to a particularly preferred embodiment, two residues aremethyl and the other two residues are either ethyl or n-propyl.

Accordingly, the present invention also relates to a process asdescribed above, wherein R₁ and R₂ are methyl and both R₃ and R₄ areeither ethyl or n-propyl or isopropyl, preferably ethyl or n-propyl.

According to the invention, in addition to the at least oneR₁R₂R₃R₄N⁺-comprising tetraalkylammonium compound, a base differing fromthis compound may be used. Examples of this base are ammonium hydroxideNH₄OH, alkali metal hydroxides or alkaline earth metal hydroxides, suchas sodium hydroxide or potassium hydroxide, or mixtures of two or moreof these compounds. In this case, the at least one R₁R₂R₃R₄N⁺-comprisingtetraalkylammonium compound contains one or more suitable anions, forexample halogen anions, such as fluoride or chloride or bromide oriodide.

According to a preferred embodiment, the at least oneR₁R₂R₃R₄N⁺-comprising tetraalkylammonium compound also contains the baseused according to (1) as an anion. Examples of basic anions in thiscontext include, inter alia, the hydroxide ion or aluminates. Aparticularly preferred basic anion is the hydroxide ion.

The present invention accordingly also relates to a process as describedabove, wherein the at least one R₁R₂R₃R₄N⁺-comprising tetraalkylammoniumcompound contains a basic anion, preferably a hydroxide ion.

The present invention therefore also relates to a process as describedabove, wherein the aqueous solution used according to (1) containsdimethyldipropylammonium hydroxide (DMDPAH) and/ordimethyldiethylammonium hydroxide (DMDEAH).

The molar ratios of silica, tetraalkylammonium compound, in particulartetraalkylammonium hydroxide compound, and water, can be adjustedsubstantially as desired, provided that it is ensured that, according to(2), at least one silicate is obtained by crystallization.

According to a preferred embodiment, the amounts of silica and/orprecursor thereof, tetraalkylammonium hydroxide compound and water usedare chosen so that the colloidal solution obtained according to (1)contains silica, tetraalkylammonium hydroxide compound and water inweight ratios in the range of 1:(0.45-0.55):(8-12). Furthermore, withregard to the abovementioned ranges, water contents up to 15 arepossible, 3 being mentioned by way of example as the lower limit.Accordingly, the colloidal solution obtained according to (1) maycontain silica, tetraalkylammonium hydroxide compound and water inweight ratios in the range of 1:(0.45-0.55):(3-15). According to theinvention, the water content may furthermore be in the range of from 4to 15 or from 5 to 15 or from 6 to 15 or from 7 to 15 or from 8 to 15 orfrom 9 to 15 or from 10 to 15 or from 11 to 15 or from 12 to 15 or from13 to 15 or from 14 to 15 or from 3 to 14 or from 3 to 13 or from 3 to12 or from 3 to 11 or from 3 to 10 or from 3 to 9 or from 3 to 8 or from3 to 7 or from 3 to 6 or from 3 to 5 or from 3 to 4. More preferredranges are, for example, from 4 to 14.5 or from 5 to 14 or from 6 to13.5 or from 7 to 13 or from 7.5 to 12.5.

For the preferred tetraalkylammonium hydroxide compounds, the presentinvention accordingly also relates to a process as described above,wherein the colloidal solution obtained according to (1) contains SiO₂,DMDPAH and/or DMDEAH and water in the weight ratios SiO₂:(DMDPAH and/orDMDEAH):water of 1:(0.45-0.55):(8-12), more preferably of1:(0.46-0.54):(8-12), more preferably of 1:(0.47-0.53):(8-12), morepreferably of 1:(0.48-0.52):(8-12) and particularly preferably of1:(0.49-0.51):(8-12). The water content in each case is more preferablyfrom 8 to 11 or from 8 to 10 or from 8 to 9 or from 9 to 12 or from 9 to11 or from 9 to 10 or from 10 to 12 or from 10 to 11 or from 11 to 12.

The present invention therefore also relates to the use of anR₁R₂R₃R₄N⁺-comprising tetraalkylammonium compound, in particular ofdimethyidipropylammonium hydroxide and/or dimethyidiethylammoniumhydroxide, preferably as a structure directing agent, in the synthesisof a silicate, preferably the hydrothermal synthesis of a silicate, thesilicate more preferably being a layered silicate or tectosilicate andthe tectosilicate more preferably being a silicate of the zeolite type.

In principle, it is possible to heat the colloidal solution obtainedaccording to (1) under any suitable pressure at any suitabletemperature, according to (2), provided that it is ensured that at leastone silicate crystallizes in the colloidal solution. Preferredtemperatures here are those which are above the boiling point of thesolution obtained according to (1) at the chosen pressure. Temperaturesup to 180° C. at normal pressure are more preferred. According to aparticularly preferred embodiment of the process of the presentinvention, the crystallization according to (2) is carried out undernormal pressure, whereas in most hydrothermal processes of the prior artthe crystallization is carried out under a pressure elevated with regardto normal pressure.

The present invention accordingly also relates to processes as describedabove, wherein the hydrothermal crystallization in (2) is carried out atnormal pressure.

The term “normal pressure” as used in the context of the presentinvention relates to a pressure of 101,325 Pa in the ideal case.However, this pressure may vary within boundaries known to the personskilled in the art. By way of example, this pressure can be in the rangeof from 95,000 to 106,000 or of from 96,000 to 105,000 or of from 97,000to 104,000 or of from 98,000 to 103,000 or of from 99,000 to 102,000 Pa.

The temperature used according to (2) at normal pressure is preferablyin the range of from 100 to 180° C., more preferably in the range offrom 110 to 175° C., more preferably in the range of from 120 to 170°C., more preferably in the range of from 130 to 165° C., andparticularly preferably in the range of from 140 to 160° C.

The present invention accordingly also relates to a process as describedabove, wherein the colloidal solution obtained according to (1) isheated at normal pressure to a temperature of in the range of from 100to 180° C., according to (2).

This temperature to which the colloidal solution obtained according to(1) is heated according to (2) can in principle be maintained until thecrystallization has taken place to the desired extent. Here, periods inthe range of up to 45 days are preferred, preferably from 12 hours to 45days, more preferably from 12 hours to 30 days, more preferably from 1to 30 days, for example about 1, 2, 5, 10, 15, 20, 25 or 30 days.

The present invention accordingly also relates to a process as describedabove, wherein the colloidal solution obtained according to (1) isheated according to (2) for a period in the range of from 12 hours to 30days.

Periods in a range of up to 12 h such as 0.5 to 12 h are alsoconceivable in the context of the process according to the presentinvention.

Any suitable compound can in principle be employed as silica or aprecursor thereof. For example, tetraalkoxysilanes, such astetraethoxysilane or tetrapropoxysilane, may be mentioned as precursorcompound. In the process of the present invention, silica as such isparticularly preferably employed rather than a silica precursor.Amorphous silica is in turn preferred.

The present invention accordingly also relates to a process as describedabove, wherein amorphous silica is employed according to (1).

Here, it is in principle possible to employ any suitable amorphoussilica. Amorphous silica having a specific surface (BET,Brunauer-Emmet-Teller; determined according to DIN 66131 by nitrogenadsorption at 77 K) in the range of from 10 to 400, preferably in therange of from 10 to 100, and particularly preferably in the range offrom 10 to 50, m²/g is preferred. Further preferred ranges are from 50to 100 m²/g or from 100 to 300 m²/g or from 300 to 400 m²/g.

According to (1), very particularly preferably DMDPAH and/or DMDEAH areemployed in addition to silica.

These compounds can be prepared by any conceivable process. According toa preferred embodiment of the process of the present invention, DMDEAHor DMDPAH is obtained by reaction of dipropylamine or diethylamine andmethyl iodide and subsequent anion exchange.

According to a more preferred embodiment, dipropylamine or diethylamineand methyl iodide are reacted with one another in a suitable solvent orsolvent mixture, preferably in ethanol. The temperature at which thisreaction is carried out is preferably in the range of from 20 to 75° C.,more preferably in the range of from 30 to 60° C., and particularlypreferably in the range of from 40 to 50° C.

According to a further embodiment of the process of the presentinvention, DMDEAH or DMDPAH can be prepared starting from dimethylamineand ethyl bromide or propyl bromide in a suitable solvent, for examplepreferably ethanol, at a suitable temperature, for example preferablyfrom 40 to 50° C.

The anion exchange according to the present invention is preferablyeffected after separation such as by filtration, centrifugation oranother solid-liquid separation process, for example preferably byfiltration, and washing of the respective ammonium hydroxide, forexample preferably with a suitable alcohol, such as ethanol, by means ofa suitable ion exchange resin, for example an Amberlyst™ resin or aresin of the type AG1-X8 (BioRad). Ion exchange using Ag₂O is alsopossible.

DMDEAH and/or DMDPAH are used in (1) preferably as a solution,particularly preferably as an aqueous solution, the concentration of theaqueous solution with respect to DMDEAH and/or DMDPAH preferably beingfrom 0.4 to 1 mol/l.

According to a particularly preferred embodiment of the process of thepresent invention, DMDPAH is employed according to (1).

The temperature during the preparation of the colloidal solutionaccording to (1) is preferably in the range of from 10 to 40° C., morepreferably in the range of from 15 to 35° C., and particularlypreferably in the range of from 20 to 30° C.

In the context of the process of the present invention, it is possibleto prepare the colloidal solution according to (1) in one step by mixingamorphous silica and tetraalkylammonium hydroxide solution.

According to a preferred embodiment of the process of the presentinvention, a colloidal solution which contains tetraalkylammoniumhydroxide, silica and water in a weight ratio of SiO₂:tetraalkylammoniumhydroxide:water of preferably 1:(0.45-0.55):(3-15), more preferably of1:(0.47-0.53):(3-15), and particularly preferably of1:(0.49-0.51):(3-15), is initially prepared in a first step. In at leastone second step, the water content of the solution obtained in the firststep is then adjusted by means of a suitable method so that it is in theabove-mentioned preferred limits.

As a suitable method preferred inter alia, the water content is adjustedby removing water in at least one suitable apparatus. The water isremoved preferably at a temperature in the range of from 60 to 85° C.,more preferably of from 65 to 80° C., and particularly preferably offrom 65 to 75° C.

The present invention accordingly also relates to the process asdescribed above, wherein, according to (1),

-   -   (i) a colloidal solution which contains tetraalkylammonium        hydroxide, silica and water in a weight ratio of        SiO₂:tetraalkylammonium hydroxide:water of preferably        1:(0.45-0.55):(3-15) is prepared and    -   (ii) the water content of the colloidal solution obtained        according to (i) is adjusted so that a colloidal solution which        contains tetraalkylammonium hydroxide, silica and water in a        weight ratio of SiO₂:tetraalkylammonium hydroxide:water of        preferably 1:(0.45-0.55):(8-12) is obtained.

Rotary evaporators or ovens may be mentioned, inter alia, as at leastone suitable apparatus. An oven is particularly preferred. Inter alia,apparatuses which permit removal of water at reduced pressure and henceat low temperatures are preferred in this context.

The heating and the subsequent preparation of the at least one silicatecan be carried out in any suitable apparatus. For example, (2) iseffected in an autoclave.

The colloidal solution is preferably suitably stirred for thecrystallization according to (2). It is also possible to rotate thereaction vessel in which the crystallization is carried out.

According to an embodiment of the process of the present invention, theat least one silicate is separated off in a suitable manner in at leastone step from the suspension obtained from (2). This separation can beeffected, for example, by means of filtration, ultrafiltration,diafiltration or centrifuging methods or, for example, spray drying andspray granulation methods. Separation by means of spray drying orfiltration is preferred.

Accordingly, the present invention also relates a process as describedabove, additionally comprising

(3) separation of the at least one silicate from the suspension obtainedaccording to (2).

According to an embodiment of the process of the present invention, thecrystallization according to (2) can be stopped by suitable quenching.Here, it is particularly preferred to add water to the suspension, saidwater being at a temperature which is suitable for stopping thecrystallization.

According to a preferred embodiment of the process of the presentinvention, the at least one silicate separated off as described above iswashed and/or dried.

Accordingly, the present invention also relates a process as describedabove, additionally comprising

(4) washing

and/or

(5) drying

of the silicate obtained according to (3).

The separation can be followed by at least one washing step and/or atleast one drying step, wherein it is possible to use identical ordifferent washing agents or washing agents mixtures in at least twowashing steps and to use identical or different drying temperatures inat least two drying steps.

The drying temperatures here are preferably in the range of from roomtemperature to 95° C., more preferably of from 40 to 90° C., morepreferably of from 50 to 85° C., more preferably in the range of from 60to 80° C., and particularly preferably in the range of from 70 to 80° C.

Accordingly, the present invention also relates a process as describedabove, wherein the silicate is washed with water according to (4) and/oris dried according to (5) at a temperature in the range of from roomtemperature to 80° C.

Washing agents which may be used are, for example, water, alcohols, suchas methanol, ethanol or propanol, or mixtures of two or more thereof.Examples of mixtures are mixtures of two or more alcohols, such asmethanol and ethanol or methanol and propanol or ethanol and propanol ormethanol and ethanol and propanol, or mixtures of water and at least onealcohol, such as water and methanol or water and ethanol or water andpropanol or water and methanol and ethanol or water and methanol andpropanol or water and ethanol and propanol or water and methanol andethanol and propanol. Water or a mixture of water and at least onealcohol, preferably water and ethanol, is preferred, water being veryparticularly preferred as the only washing agent.

According to the process of the present invention, a silicate, inparticular a layered silicate, is obtained.

The present invention accordingly also relates to a silicate, inparticular a layered silicate, obtainable by the process describedabove.

The present invention also relates to the silicate per se, wherein, inthe X-ray diffraction pattern by Cu K alpha 1 radiation, at least thefollowing reflections occur: Intensity [%] Diffraction angle 2θ/° [Cu K(alpha 1)] 100 8.0-8.4 11-21 11.0-11.4 13-23 13.2-13.6  5-15 18.0-18.4 7-17 18.4-18.8 19-29 19.9-20.0wherein 100% relates to the intensity of the maximum peak in the X-raydiffraction pattern.

In particular, the present invention relates to the silicate per se,wherein, in the X-ray diffraction pattern by Cu K alpha 1 radiation, atleast the following reflections occur: Intensity [%] Diffraction angle2θ/° [Cu K (alpha 1)] 100 8.0-8.4 11-21 11.0-11.4 13-23 13.2-13.6  5-1518.0-18.4  7-17 18.4-18.8 19-29 19.8-20.2 20-30  22.0-22.35  6-1622.36-22.7  23-33  23.3-23.59 22-32 23.60-23.8 

The layered silicates according to the invention or layered silicatesprepared according to the invention preferably have the space group P2/c. If, as described above, tetraalkylammonium hydroxide and silicaand/or silica precursor were used as starting materials, the layeredsilicates prepared according to the invention preferably have thefollowing lattice parameters, determined by Rietveld analysis:

-   -   a=7.33(1) Å    -   b=10.72(1) Å    -   c=17.51(1) Å    -   beta=115.7(1)°.

The Rietveld analysis is described in R. A. Young (editor), The RietveldMethod, Oxford University Press, 1995, Oxford, in particular in Chapter7: Analytical profile fitting of X-ray powder diffraction profiles inRietveld analysis, pages 111-131.

According to 29-Si MAS NMR spectroscopy, the layered silicates accordingto the invention have a low field signal at about 104 ppm, which ischaracteristic of a silanol group typical of layered silicates.

According to 1-H NMR spectroscopy, the layered silicates according tothe invention have a low field signal at about 16.4 ppm, which ischaracteristic of a silanol group typical of layered silicates.

The given chemical shifts are based on TMF as an internal standard.

According to a particularly preferred embodiment of the process of thepresent invention, the silicate obtained according to (2) is calcinedaccording to (6) in at least one additional step.

It is in principle possible to subject the suspension comprising the atleast one silicate directly to calcination. Preferably, the silicate isseparated off from the suspension, as described above according to (3),before the calcination.

Before the calcination, the silicate separated off from the suspensioncan be subjected to at least one washing step (4) as described aboveand/or at least one drying step (5) as described above. Preferably, thesilicate separated off from the suspension is dried and is fed to thecalcination without a washing step.

The calcination according to (6) of the silicate obtained according to(2) and/or (3) and/or (4) and/or (5) is preferably effected at atemperature in the range of up to 600° C. to give a tectosilicate.

Thereby, according to a preferred embodiment of the process of thepresent invention, the heating of the silicate is carried out from roomtemperature to a temperature of up to 600° C., the heating rate furtherpreferably being in the range of from 0.1 to 12° C./h, more preferablyof from 1 to 11° C./h, and particularly preferably in the range of from5 to 10° C./h.

Calcination temperatures of from 300 to 600° C. are particularlypreferred.

According to a possible embodiment of the process of the presentinvention, the calcination is carried out stepwise at successivetemperatures. The term “stepwise at successive temperatures” as used inthe context of the present invention refers to a calcination in whichthe silicate to be calcined is heated to a certain temperature, is keptat this temperature for a certain time, and is heated from thistemperature to at least one further temperature and is once again keptthere for a certain time.

The silicate to be calcined is preferably kept at up to 4, morepreferably at up to 3, particularly preferably at 2 temperatures.

In this respect, the first temperature is preferably in the range offrom 500 to 540° C., more preferably in the range of from 500 to 535°C., more preferably in the range of from 510 to 530° C., andparticularly preferably in the range of from 515 to 525° C. Thistemperature is preferably kept for a period of from 8 to 24 h, morepreferably from 9 to 18 h, and in particular from 10 to 14 hours.

The second temperature is preferably in the range of from greater than540 to 600° C., more preferably in the range of from 550 to 580° C., andparticularly preferably in the range of from 555 to 570° C. Thistemperature is preferably kept for a period in the range of from 0.5 to6 h, more preferably of from 1 to 4 h, and in particular of from 1 to 3hours.

Accordingly, the present invention also relates to a process asdescribed above, wherein the calcination is effected stepwise atsuccessive temperatures in the range of up to 600° C., preferably from300 to 600° C.

The calcination can be effected in any suitable atmosphere, for exampleair, lean air, nitrogen, steam, synthetic air or carbon dioxide. Thecalcination is preferably effected under air.

The calcination can be carried out in any apparatus suitable for thispurpose. The calcination is preferably effected in a rotating tube, in abelt calciner, in a muffle furnace, or in situ in an apparatus in whichthe silicate is subsequently used for the intended purpose, for exampleas a molecular sieve or for another application described below. Arotating tube and a belt calciner are particularly preferred here.

According to the process of the present invention, a silicate, inparticular a tectosilicate, is obtained.

Accordingly, the present invention also relates to a process asdescribed above, additionally comprising

(6) calcination of the silicate obtained according to (2) and

-   -   optionally separated off according to (3) and    -   optionally washed according to (4) and/or dried according to (5)        to give a tectosilicate.

The present invention accordingly also relates to a silicate, inparticular a tectosilicate, obtainable by the process described above,comprising the calcination according to (6), in particular thetectosilicate obtainable using DMDEAH and/or DMDPAH.

The present invention also relates to a silicate per se, wherein, in theX-ray diffraction pattern by Cu K alpha 1 radiation, at least thefollowing reflections occur: Intensity [%] Diffraction angle 2θ/° [Cu K(alpha 1)] 100  9.8-10.2 24-34 11.0-11.4  9-19 15.5-15.9 12-22 19.4-19.619-29 19.6-19.8wherein 100% relates to the intensity of the maximum peak in the X-raydiffraction pattern.

In particular, the present invention relates to the tectosilicate perse, wherein, in the X-ray diffraction pattern by Cu K alpha 1 radiation,at least the following reflections occur: Intensity [%] Diffractionangle 2θ/° [Cu K (alpha 1)] 100  9.8-10.2 24-34 11.0-11.4  9-1915.5-15.9 12-22 19.4-19.6 19-29 19.6-19.8  8-18  26.2-<26.3  8-18 26.3-<26.4 13-23 26.4-26.6

The tectosilicates of the present invention or tectosilicates preparedaccording to the invention preferably have the space group P 2/c. If, asdescribed above, tetraalkylammonium hydroxide and silica and/or silicaprecursor were used as starting materials, the tectosilicates preparedaccording to the invention preferably have the following latticeparameters, determined by Rietveld analysis:

-   -   a=7.34(1) Å    -   b=8.72(1) Å    -   c=17.17(1) Å    -   beta=114.2(1)°.

According to 29-Si MAS NMR spectroscopy, the low field signal at about104 ppm which is found in the case of the layered silicates of thepresent invention described above and which is characteristic of asilanol group typical of layered silicates, is absent in the case of thenovel tectosilicates.

The novel tectosilicates preferably have 8 MR and 10 MR channels, the 8MR channels particularly preferably being parallel to c of the unitcell, as stated above, and the 10 MR channels particularly preferablybeing parallel to a of the unit cell, as stated above. Regarding thedefinition of the 8 MR and 10 MR channels, reference is made to Ch.Baerlocher, W. M. Meier, D. H. Olson, Atlas of Zeolite Framework Types,5th Edition, 2001, Elsevier, pages 10-15.

In particular, the tectosilicates of the present invention arecharacterized in that they have a substantially monomodal distributionwith respect to the two-dimensional 8 MR and 10 MR channel porestructure. The pore openings both of the 8 MR and of the 10 MR channelseach have in this respect an area preferably in the range of(5.70-6.00)×(4.00-4.20) Å², particularly preferably of(5.80-5.90)×(4.05-4.15) Å².

The tectosilicates of the present invention preferably have microporeshaving a specific surface in the range of greater than 200 m²/g, morepreferably of from greater than 200 to 800 m²/g, more preferably of from300 to 700 m²/g, and particularly preferably of from 400 to 600 m²/g,determined in each case according to DIN 66135 (Langmuir).

The tectosilicates of the present invention preferably have pores havinga pore volume in the range of from 0.15 to 0.21 ml/g, more preferably offrom 0.16 to 0.20 ml/g, and particularly preferably of from 0.17 to 0.19ml/g, determined in each case according to DIN 66134.

Accordingly, the tectosilicates of the present invention are silicatesof a microporous zeolitic type.

The thermal stability of the tectosilicates of the present invention ispreferably at least 600° C., more preferably more than 600° C.

The term “thermal stability” as used in this context for the purposes ofthe present invention denotes the temperature at which the specificlattice structure of the tectosilicate is preserved under atmosphericpressure.

According to further embodiments of the present invention, it ispossible for the silicates prepared according to the invention tocontain at least one atom of at least one other element in addition tosilicon and oxygen. Thus, it is possible to incorporate at least oneatom of at least one of the elements aluminum, boron, iron, titanium,tin, germanium, zirconium, vanadium or niobium into the silicatestructure.

If, for example, aluminum is incorporated, it is possible to use, forexample, metallic aluminum or suitable aluminates, such as alkali metalaluminates, and/or aluminum alcoholates, such as aluminumtriisopropylate, in addition to the tetraalkylammonium compound and thesilica and/or silica precursor as starting materials.

If, for example, boron is incorporated, it is possible to use, forexample, free boric acid and/or borates and/or boric esters, such astriethyl borate, in addition to the tetraalkylammonium compound and thesilica and/or silica precursor as starting materials.

If, for example, titanium is incorporated, it is possible to use, forexample, titanium alcoholates, such as titanium ethanolates or titaniumpropylates, in addition to the tetraalkylammonium compounds and thesilica and/or silica precursor as starting materials.

If, for example, tin is incorporated, it is possible to use, forexample, tin chlorides and/or organometallic tin compounds, such as tinalcoholates, or chelates, such as tin acetylacetonates, in addition tothe tetraalkylammonium compound and the silica and/or silica precursoras starting materials.

If, for example, zirconium is incorporated, it is possible to use, forexample, zirconium chloride and/or zirconium alcoholates in addition tothe tetraalkylammonium compound and the silica and/or silica precursoras starting materials.

If, for example, vanadium or germanium or niobium is incorporated, it ispossible to use, for example, vanadium chloride or germanium chloride orniobium chloride in addition to the tetraalkylammonium compound and thesilica and/or silica precursor as starting materials.

Accordingly, the present invention also relates to a process asdescribed above and to the layered silicates and/or the tecosilicates asdescribed above, in particular the tectosilicates as described above,wherein the silicates additionally contain at least one of the elementsAl, B, Fe, Ti, Sn, Ge, Zr, V or Nb in addition to Si and O.

Depending on the type of atoms which are incorporated into the lattice,a negatively charged framework which makes it possible, for example, toload the silicate with cations may form. Inter alia, the ammonium ionsR₁R₂R₃R₄N⁺ of the template compounds, platinum, palladium, rhodium orruthenium cations, gold cations, alkali metal cations, for examplesodium or potassium ions, or alkaline earth metal cations, for examplemagnesium or calcium ions, may be mentioned as such.

In many technical applications, the user often desires to employ thecrystalline material which has been processed to moldings, instead ofthe crystalline material as such. Such moldings are necessary inparticular in many industrial processes, in order, for example, to beable to expediently operate separations of substances from mixtures in,for example, tube reactors.

The present invention accordingly also relates to a molding comprisingthe crystalline, microporous tectosilicate described above. The presentinvention also comprises moldings comprising the layered silicatedescribed above.

In general, the molding may comprise all conceivable further compoundsin addition to the tectosilicate of the present invention, provided thatit is ensured that the resulting molding is suitable for the desiredapplication.

In the context of the present invention, it is preferred if at least onesuitable binder material is used in the production of the molding. Inthe context of this preferred embodiment, more preferably a mixture oftectosilicate and the at least one binder is prepared.

Accordingly, the present invention also describes a process for theproduction of a molding containing a tectosilicate as described above,comprising the step

-   -   (I) preparation of a mixture containing a tectosilicate as        described above or a tectosilicate obtainable by a process as        described above, and at least one binder material.

Suitable binders are in general all compounds which impart adhesionand/or cohesion between the particles of the tectosilicate which are tobe bound, over and above the physisorption which may be present withouta binder. Examples of such binders are metal oxides, such as SiO₂,Al₂O₃, TiO₂, ZrO₂ or MgO, or clays or mixtures of two or more of thesecompounds.

As Al₂O₃ binders, clay minerals and naturally occurring or syntheticaluminas, for example alpha-, beta-, gamma-, delta-, eta-, kappa-, chi-or theta-alumina and the inorganic or organometallic precursor compoundsthereof, such as gibbsite, bayerite, boehmite, pseudoboehmite ortrialkoxyaluminates, such as aluminum triisopropylate are preferred inparticular. Further preferred binders are amphiphilic compounds having apolar and a nonpolar moiety, and graphite. Further binders are, forexample, clays, such as montmorillonites, kaolins, bentonites,halloysites, dickites, nacrites or anaxites.

These binders can be used as such. In the context of the presentinvention, it is also possible to use compounds from which the binder isformed in at least one further step in the production of the moldings.Examples of such binder precursors are tetraalkoxysilanes,tetraalkoxytitanates, tetraalkoxyzirconates or a mixture of two or moredifferent tetraalkoxysilanes or a mixture of two or more differenttetraalkoxytitanates or a mixture of two or more differenttetraalkoxyzirconates or a mixture of at least one tetraalkoxysilane andat least one tetraalkoxytitanate or of at least one tetraalkoxysilaneand at least one tetraalkoxyzirconate or of at least onetetraalkoxytitanate and at least one tetraalkoxyzirconate or a mixtureof at least one tetraalkoxysilane and at least one tetraalkoxytitanateand at least one tetraalkoxyzirconate.

In the context of the present invention, binders which either completelyor partly consist of SiO₂ or are a precursor of SiO₂, from which SiO₂ isformed in at least one further step in the production of the moldingsare very particularly preferred. In this context, both colloidal silicaand “wet process” silica as well as “dry process” silica can be used.These are very particularly preferably amorphous silica, the size of thesilica particles being, for example, in the range of from 5 to 100 nmand the surface of the silica particles being in the range of from 50 to500 m²/g.

Colloidal silica, preferably in the form of an alkaline and/orammoniacal solution, more preferably in the form of an ammoniacalsolution, is, for example, commercially available as, inter alia,Ludox®, Syton®, Nalco® or Snowtex®.

“Wet process” silica is, for example, commercially available, interalia, as Hi-Sil®, Ultrasil®, Vulcasil®, Santocel®, Valron-Estersil®,Tokusil® or Nipsil®.

“Dry process” silica is, for example, commercially available, interalia, as Aerosil®, Reolosil®, Cab-O-Sil®, Fransil® or ArcSilica®.

In the context of the present invention, inter alia an ammoniacalsolution of colloidal silica is preferred.

Accordingly, the present invention also describes a molding as describedabove, additionally comprising SiO₂ as binder material.

The present invention also relates to a process as described above, thebinder used according to (I) being a SiO₂-containing or SiO₂-formingbinder.

Accordingly, the present invention also describes a process as describedabove, the binder being a colloidal silica.

The binders are preferably used in an amount which leads to the finallyresulting moldings whose binder content is up to 80% by weight, morepreferably in the range of from 5 to 80% by weight, more preferably inthe range of from 10 to 70% by weight, more preferably in the range offrom 10 to 60% by weight, more preferably in the range of from 15 to 50%by weight, more preferably in the range of from 15 to 45% by weight,particularly preferably in the range of from 15 to 40% by weight, basedin each case on the total weight of the finally resulting molding.

The term “finally resulting molding” as used in the context of thepresent invention relates to a molding as obtained from the drying andcalcining steps (IV) and/or (V), as described below, particularlypreferably obtained from (V).

The mixture of binder or precursor of a binder and a zeolitic materialcan be mixed with at least one further compound for further processingand for the formation of a plastic material. Here, inter alia, poreformers may preferably be mentioned.

In the process of the present invention, all compounds which, withregard to the finished molding, provide a certain pore size and/or acertain pore size distribution and/or certain pore volumes can be usedas pore formers.

Preferably used pore formers in the process of the present invention arepolymers which are dispersible, suspendable or emulsifiable in water orin aqueous solvent mixtures. Preferred polymers here are polymeric vinylcompounds, for example polyalkylene oxides, such as polyethylene oxides,polystyrene, polyacrylates, polymethacrylates, polyolefins, polyamidesand polyesters, carbohydrates, such as cellulose or cellulosederivatives, for example methylcellulose, or sugars or natural fibers.Further suitable pore formers are, for example, pulp or graphite.

If pore formers are used in the preparation of the mixture according to(I), the pore former content, preferably the polymer content of themixture according to (I) is preferably in the range of from 5 to 90% byweight, preferably in the range of from 15 to 75% by weight, andparticularly preferably in the range of from 25 to 55% by weight, basedin each case on the amount of novel tectosilicate in the mixtureaccording to (I).

If desired for the pore size distribution to be achieved, a mixture oftwo or more pore formers may also be used.

In a particularly preferred embodiment of the process of the presentinvention, as described below, the pore formers are removed in a step(V) by calcination to give the porous molding. According to a preferredembodiment of the process of the invention, moldings which have pores inthe range of at least 0.6 ml/g, preferably in the range of from 0.6 to0.8 ml/g, and particularly preferably in the range of from more than 0.6to 0.8 ml/g, determined according to DIN 66134, are obtained thereby.

The specific surface of the novel moldings is in general at least 350m²/g, preferably at least 400 m²/g, and particularly preferably at least425 m²/g, determined according to DIN 66131. For example, the specificsurface may be in the range of from 350 to 500 m²/g or of from 400 to500 m²/g or of from 425 to 500 m²/g.

Accordingly, the present invention also describes a molding as describedabove, having a specific surface of at least 350 m²/g, comprising poreshaving a pore volume of at least 0.6 ml/g.

In the context of a likewise preferred embodiment of the presentinvention, at least one pasting agent is added in the preparation of themixture according to (I).

Pasting agents which may be used are all compounds suitable for thispurpose. These are preferably organic, in particular hydrophilicpolymers, for example cellulose, cellulose derivatives, such asmethylcellulose, starch, such as potato starch, wallpaper paste,polyacrylates, polymethacrylates, polyvinyl alcohol,polyvinylpyrrolidone, polyisobutene or polytetrahydrofuran.

Accordingly, in particular compounds which also act as pore formers canbe used as pasting agents.

In a particularly preferred embodiment of the process of the presentinvention as described below, these pasting agents are removed in a step(V) by calcination to give the porous molding.

According to a further embodiment of the present invention, at least oneacidic additive is added during the preparation of the mixture accordingto (I). Organic acidic compounds which can be removed in the preferredstep (V), as described below, by calcination are very particularlypreferred. Carboxylic acids, for example formic acid, oxalic acid and/orcitric acid, are particularly preferred. It is also possible to use twoor more of these acidic compounds.

The order of addition of the components of the mixture according to (I)which contains the tectosilicate is not critical. It is both possiblefirst to add the at least one binder, then the at least one pore formerand the at least one acidic compound and finally the at least onepasting agent and to interchange the sequence with regard to the atleast one binder, the at least one pore former, the at least one acidiccompound and the at least one pasting agent.

After the addition of the binder to the tectosilicate solid, to which,if appropriate, at least one of the compounds described above havealready been added, the mixture according to (I) is, as a rule,homogenized for from 10 to 180 minutes. Inter alia, kneaders, edge millsor extruders are particularly preferably used for the homogenization.The mixture is preferably kneaded. On the industrial scale, treatment inan edge mill is preferably employed for the homogenization.

Accordingly, the present invention also describes a process as describedabove, comprising the steps

-   -   (I) preparation of a mixture containing a tectosilicate as        described above or a tectosilicate obtainable by a process as        described above, and at least one binder;    -   (II) kneading of the mixture.

The homogenization is carried out as a rule at temperatures in the rangeof from about 10° C. to the boiling point of the pasting agent andnormal pressure or slightly superatmospheric pressure. Thereafter, ifappropriate, at least one of the compounds described above can be added.The mixture thus obtained is homogenized, preferably kneaded, until anextrudable plastic material has formed.

According to a more preferred embodiment of the invention, thehomogenized mixture is molded.

In the context of the present invention, those processes in which themolding is effected by extrusion in conventional extruders, for exampleto give extrudates having a diameter of preferably from 1 to 10 mm,particularly preferably from 2 to 5 mm, are preferred for the shapingprocesses. Such extrusion apparatuses are described, for example, inUllmann's Enzyklopadie der Technischen Chemie, 4th Edition, Vol. 2, page295 et seq., 1972. In addition to the use of a screw-type extruder, aplunger-type extruder is also preferably used for the molding.

In principle, however, all known and/or suitable kneading and moldingapparatuses and processes may be used for the shaping. Examples of theseare inter alia:

-   -   (i) briquetting, i.e. mechanical compression with or without        addition of additional binder material;    -   (ii) pelleting, i.e. compacting by circular and/or rotational        movements;    -   (iii) sintering, i.e. the material to be molded is subjected to        a thermal treatment.

For example, the shaping can be selected from the following group, thecombination of at least two of these methods being explicitly included:briquetting by treatment in a ram press, treatment in a roll press ortreatment in a ring-roll press, briquetting without a binder; pelleting,melting, spinning techniques, deposition, foaming, spray drying; firingin a shaft furnace, convection oven, moving grate or rotary kiln,treatment in an edge mill.

The compacting may take place at ambient pressure or at a pressure aboveambient pressure, for example in a pressure range from 1 to severalhundred bar. Furthermore, the compacting may take place at ambienttemperature or at a temperature above ambient temperature, for examplein a temperature range from 20 to 300° C. If drying and/or firing arepart of the shaping step, temperatures up to 600° C. are conceivable.Finally, the compacting may take place in the ambient atmosphere or in acontrolled atmosphere. Controlled atmospheres are, for example, inertgas atmospheres and reducing and/or oxidizing atmospheres.

Accordingly, the present invention also describes a process for theproduction of a molding as described above, comprising the steps

-   -   (I) preparing of a mixture containing a tectosilicate as        described above or a tectosilicate obtainable by a process as        described above, and at least one binder;    -   (II) kneading of the mixture;    -   (III) molding of the kneaded mixture to give at least one        molding.

The shape of the moldings produced according to the invention can bechosen as desired. In particular, inter alia spheres, oval shapes,cylinders or tablets are possible.

In the context of the present invention, molding by extrusion of thekneaded mixture obtained according to (II) is particularly preferablycarried out, more preferably substantially cylindrical extrudates havinga diameter of from 1 to 20 mm, preferably in the range of from 1 to 10mm, more preferably in the range of from 2 to 10 mm and more preferablyin the range of from 2 to 5 mm, being obtained as extrudates.

In the context of the present invention, step (III) is preferablyfollowed by at least one drying step. This at least one drying step iseffected at temperatures in the range of, in general, from 80 to 160°C., preferably from 90 to 145° C., particularly preferably from 100 to130° C., the duration of drying generally being 6 hours or more, forexample from 6 to 24 hours. However, depending on the moisture contentof the material to be dried, shorter drying times, for example about 1hour or 2, 3, 4 or 5 hours, are also possible.

Before and/or after the drying step, the preferably obtained extrudatecan, for example, be comminuted. Granules or chips having a particlediameter of from 0.1 to 5 mm, in particular from 0.5 to 2 mm, arepreferably obtained.

Accordingly, the present invention also describes a process for theproduction of a molding as described above, comprising the step

-   -   (I) preparing of a mixture containing a tectosilicate as        described above or a tectosilicate obtainable by a process as        described above, and at least one binder;    -   (II) kneading of the mixture;    -   (III) molding of the kneaded mixture to give at least one        molding;    -   (IV) drying of the at least one molding.

In the context of the present invention, the step (IV) is preferablyfollowed by at least one calcination step. The calcination is carriedout at temperatures in the range of, in general, from 350 to 750° C.,preferably from 450 to 600° C.

The calcination can be effected under any suitable gas atmosphere, airand/or lean air being preferred. Furthermore, the calcination ispreferably carried out in a muffle furnace, a rotary kiln and/or a beltcalcination oven, the duration of calcination generally being 1 hour ormore, for example from 1 to 24 hours or from 3 to 12 hours. Accordingly,for the purposes of the process of the present invention, it ispossible, for example, to calcine the molding once, twice or more oftenfor, in each case, at least 1 hour, for example in each case from 3 to12 hours, it being possible for the temperatures during a calcinationstep to remain constant or to be changed continuously ordiscontinuously. If calcination is effected twice or more often, thecalcination temperatures can be different or identical in the individualsteps.

Accordingly, the present invention also relates to a process for theproduction of a molding as described above, comprising the steps

-   -   (I) preparing of a mixture containing a tectosilicate as        described above or a tectosilicate obtainable by a process as        described above, and at least one binder;    -   (II) kneading of the mixture;    -   (III) molding of the kneaded mixture to give at least one        molding;    -   (IV) drying of the at least one molding;    -   (V) calcining of the at least one dried molding.

After the calcination step, the calcined material can, for example, becomminuted. Granules or chips having a particle diameter of from 0.1 to5 mm, in particular from 0.5 to 2 mm, are preferably obtained.

Before and/or after the drying and/or before and/or after thecalcination, the at least one molding can, if appropriate, be treatedwith a concentrated or dilute Broenstedt acid or a mixture of two ormore Broenstedt acids. Suitable acids are, for example, hydrochloricacid, sulfuric acid, phosphoric acid, nitric acid or carboxylic acids,dicarboxylic acids or oligo- or polycarboxylic acids, such asnitrilotriacetic acid, sulfosalicylic acid or ethylenediaminetetraaceticacid.

If appropriate, this at least one treatment with at least one Broenstedtacid is followed by at least one drying step and/or at least onecalcination step, which in each case is carried out under the conditionsdescribed above.

According to a further embodiment of the process of the presentinvention, the moldings obtained according to the invention can, forbetter hardening, be subjected to a water steam treatment, after whichpreferably drying is effected at least once again and/or calcination iseffected at least once again. For example, after at least one dryingstep and at least one subsequent calcination step, the calcined moldingis subjected to the steam treatment and is then dried at least onceagain and/or calcined at least once again.

The moldings obtained according to the invention have hardnesses whichare in general in the range of from 2 to 15 N, preferably in the rangeof from 5 to 15 N, particularly preferably in the range of from 10 to 15N.

Accordingly, the present invention also relates to a molding asdescribed above, having a cutting hardness in the range of from 2 to 15N.

In the context of the present invention, the hardness described abovewas determined on an apparatus from Zwick, type BZ2.5/TS1S, with apreliminary force of 0.5 N, a preliminary force feed rate of 10 mm/minand a subsequent test speed of 1.6 mm/min. The apparatus had astationary turntable and a freely movable ram with a built-in blade of0.3 mm thickness. The movable ram with the blade was connected to a loadcell for force transduction and moved during the measurement toward thestationary turntable on which the catalyst molding to be investigatedrested. The tester was controlled by means of a computer which recordedand evaluated the results of the measurements. The values obtained arethe mean value of the measurements for, in each case, 10 catalystmoldings. The catalyst molding had a cylindrical geometry, their meanlength corresponding to about twice to three times the diameter, andwere loaded with the blade of 0.3 mm thickness with increasing forceuntil the molding had been cut through. The blade was applied to themolding perpendicularly to the longitudinal axis of the molding. Theforce required for this purpose is the cutting hardness (unit N).

The present invention moreover relates to the use of the silicates ofthe invention, in particular of the novel tectosilicates, and/or of themoldings of the invention, as a molecular sieve, catalyst, catalystsupport or binder thereof, as adsorbents, pigments, additives indetergents, an additive for building materials, for impartingthixotropic properties to coating pastes and finishes, and applicationsas external and internal lubricant, as flameproofing agent, auxiliaryagent and filler in paper products, in bactericidal and/or fungicidaland/or herbicidal compositions, for ion exchange, for the production ofceramics, in polymers, in electrical, optical or electroopticalcomponents and switching elements or sensors.

Reactions which can be catalyzed by the silicates of the invention are,for example, hydrogenations, dehydrogenations, oxydehydrogenations,oxidations, epoxidations, polymerization reactions, aminations,hydrations and dehydrations, nucleophilic and electrophilic substitutionreactions, addition and elimination reactions, double bond and skeletalisomerizations, dehydrocyclizations, hydroxylations or heteroaromatics,epoxide-aldehyde rearrangement reactions, metathesis, olefin preparationfor methanol, Diels-Alder reactions, formation of carbon-carbon bonds,for example olefin dimerization or olefin trimerization, andcondensation reactions of the aldol condensation type. Depending on themolecule to be reacted, the catalytic reactions can be carried out inthe gas or liquid phase or in the supercritical phase.

The silicates of the present invention are also particularly suitable asa molecular sieve. Here, the high internal surface of the material ofthe invention can be advantageously utilized, as well as separatingmolecules from one another on the basis of their difference in molecularsize. Depending on the separation task, the respective adsorption can beeffected in the gas phase or the liquid phase or in the supercriticalphase.

In a first embodiment, the novel silicates are suitable for separatingconstitutional isomers, for example for separating n- and iso-isomers ofsmall molecules. In the context of the present invention, the term“small molecule” is understood as molecules having a kinetic diameter inthe range of from 3.5 to 5.5 Å. For the definition of the kineticdiameter, reference may be made to D. W. Breck, Zeolite MolecularSieves, 1974, J. Wiley, pages 634-641.

Separation of n-butane and isobutane may be mentioned by way of examplein this context.

In a second embodiment, the silicates of the invention are suitable forthe separation of configurational isomers, for example for theseparation of cis-butene and trans-butene.

The present invention relates very generally to the use of the silicatesof the invention, in particular of the tectosilicates, for theseparation of at least one alkane and/or at least one alkene and/or atleast one alkyne from a mixture containing at least two alkanes or atleast two alkenes or at least two alkynes or at least one alkane and atleast one alkene or at least one alkane and at least one alkyne or atleast one alkene and at least one alkyne or at least one alkane and atleast one alkene and at least one alkyne, in particular for theseparation of constitutional isomers and/or configurational isomers, theat least one alkane and/or at least one alkene and/or at least onealkyne having up to 10 carbon atoms, for example one carbon atom in thecase of methane or 2, 3, 4, 5, 6, 7, 8, 9 or 10 carbon atoms.

The present invention preferably relates to the use of the silicates ofthe invention, in particular of the tectosilicates, for the separationof at least one alkane and/or at least one alkene and/or at least onealkyne from a gas mixture containing at least two alkanes or at leasttwo alkenes or at least two alkynes or at least one alkane and at leastone alkene or at least one alkane and at least one alkyne or at leastone alkene and at least one alkyne or at least one alkane and at leastone alkene and at least one alkyne, in particular for the separation ofconstitutional isomers and/or configurational isomers.

Particularly preferred fields of use are the separation of methane andethane or the separation of ethene, propene and butene, in particulartrans-2-butene, or the separation of butane and butene or the separationof n-butane and isobutane or the separation of 1-butene andtrans-2-butene.

The silicates of the invention therefore permit an easy separation ofmixtures which have a narrow boiling range, which cannot be separated bydistillative methods without large apparatuses or without the aid ofadditives. This makes it possible to reduce costs in chemical productionprocesses. In such processes, the tectosilicate of the invention as suchor preferably in the form of moldings is used in at least one suitableapparatus, for example a tubular reactor, through which the mixture tobe separated is passed continuously or batchwise, preferablycontinuously.

The present invention accordingly also relates to an apparatus, inparticular a tubular reactor, comprising at least one tectosilicate asdescribed above and/or a molding as described above for the separationof a mixture, in particular for the separation of at least one alkaneand/or at least one alkene and/or at least one alkyne from a gas mixturecontaining at least two alkanes or at least two alkenes or at least twoalkynes or at least one alkane and at least one alkene or at least onealkane and at least one alkyne or at least one alkene and at least onealkyne or at least one alkane and at least one alkene and at least onealkyne.

According to a particularly preferred embodiment, such a tubular reactorhas a length:width ratio greater than or equal to, preferably greaterthan 3:1.

Likewise, the silicate of the present invention or the silicate preparedaccording to the present invention, in particular the tectosilicate orthe moldings containing said silicate, can be also used, for example,

-   -   for the separation of olefin and carbondioxide, for example for        the purification of polyethylene or polypropylene,    -   or as amination catalyst, for example for the preparation of        methyl amine and/or dimethyl amine from methanol and ammonia or        from synthesis gas and ammonia wherein a low fraction of        trimethylamine is preferably obtained,    -   or for polymerizations such as for the preparation of        polytetrahydrofuran from tetrahydrofuran,    -   or as hydroxylation catalyst such as for the preparation of        phenol from benzene,    -   or generally as reaction catalyst for conversions of 6-ring        aromatic compounds,    -   or for the conversion of cyclohexanone to cyclohexanone oxime,    -   or for Beckmann re-arrangements such as for the conversion of        cyclohexanone oxime to caprolactam.

Surprisingly, it was found that the novel material, in particular thenovel tectosilicate having the structure RUB41, has a very high uptakecapacity for 6-ring aromatic or heteroaromatic compounds, especiallybenzene. Therefore, it is envisaged to use the novel material also forthe separation of benzene from mixtures containing benzene.

If the novel tectosilicate or the molding containing this tectosilicateis used as an adsorbent, for example for the separation of substances,the desorption of the adsorbed compound or of the adsorbed compounds canbe effected by a suitable reduction of the pressure and/or a suitabletemperature change, particularly preferably by a suitable temperatureincrease and/or by bringing the tectosilicate or the molding containingthis tectosilicate into contact with at least one compound which adsorbsmore strongly than the compound to be desorbed or compounds to bedesorbed.

Depending on the method of use of the tectosilicate of the invention itmay be necessary to regenerate the tectosilicate or the moldingcontaining the tectosilicate after a certain time of use.

In a further embodiment of the process of the present invention, thetectosilicate and/or the molding are regenerated after the use in therespective technical field by a process in which the regeneration iseffected by controlled burning off of the deposits responsible for thedecreasing performance. An inert gas atmosphere which contains exactlydefined amounts of oxygen-donating substances is preferably employed forthis purpose. Such a regeneration process is described, inter alia, inWO 98/55228 and DE 197 23 949 A1, particularly in column 2, lines 33 to54 of DE 197 23 949 A1, the relevant disclosure of which is herebyincorporated by reference in its entirety in the subject of the presentapplication.

The tectosilicate to be regenerated and/or the moldings are heated to atemperature in the range of from 250 to 600° C., preferably of from 400to 550° C., in particular of from 450 to 500° C., either in theapparatus, for example the tubular reactor, or in an external oven, inan atmosphere which contains from 0.1 to about 20 parts by volume ofoxygen-donating substances, particularly preferably from 0.1 to 20 partsby volume of oxygen. The heating is preferably carried out at a heatingrate of from 0.1 to 20° C./min, preferably from 0.3 to 15° C./min, andin particular from 0.5 to 10° C./min.

During this heating phase, heating is effected to a temperature at whichmost organic deposits begin to decompose while at the same time thetemperature is controlled via the oxygen content and therefore does notincrease in a manner such that the tectosilicate structure and/ormolding structure is damaged. The slow increase in the temperature orthe residence at low temperature by establishing the correspondingoxygen content and the corresponding heating power is a substantial stepfor preventing local overheating of the tectosilicate and/or of themoldings at high organic loads.

If the temperature of the waste gas stream at the reactor exit decreasesin spite of increasing amounts of oxygen-donating substances in the gasstream, burning off of the organic deposits is complete. The duration ofthe treatment is generally in each case from 1 to 30, preferably fromabout 2 to about 20, in particular from about 3 to about 10 hours.

The subsequent cooling of the tectosilicate regenerated in this mannerand/or of the molding is preferably carried out in a manner such thatthe cooling does not take place too rapidly, since otherwise themechanical strength, for example of the moldings, may be adverselyaffected.

It may be necessary to follow the regeneration carried out bycalcination, as described above, with washing with water and/or diluteacids, for example hydrochloric acid, in order to remove any inorganicload (traces of alkali, etc.) remaining as a result of contamination ofthe starting materials. Further drying and/or further calcination canthen be carried out.

According to a further embodiment of the process of the presentinvention, the tectosilicate at least partly deactivated for therespective technical field of use and/or the moldings can be washed witha solvent in the reaction reactor or in an external reactor in order toremove desired product which is still adhering, before the heatingaccording to the regeneration procedure. The washing is carried out herein a manner such that, although the respective adhering desired productscan be removed, temperature and pressure are not chosen to be so highthat most organic deposits are likewise removed. Preferably, onlywashing with a suitable solvent is carried out. Thus, all solvents inwhich the respective desired product is readily soluble are suitable forthis wash process. The amount of solvent used and the duration of thewash process are not critical. The wash process can be repeated severaltimes and can be carried out at elevated temperatures. With the use ofCO₂ as a solvent, supercritical pressure is preferred; otherwise, thewash process can be effected under normal pressure or elevated pressureor supercritical pressure. After the end of the wash process, drying isgenerally effected. Although the drying process is in general notcritical, the drying temperature should not too greatly exceed theboiling point of the solvent used for the washing, in order to avoidabrupt vaporization of the solvent in the pores, in particular in themicropores, since this too may lead to damage to the lattice structure.

For process optimization, it is possible to use at least two apparatuseswhich in each case contain the tectosilicate of the present inventionand/or the moldings of the present invention, in the case of theregeneration at least one apparatus being taken out of operation and atleast one apparatus remaining in operation so that the process does nothave to be interrupted at any time.

The present invention is explained in more detail with reference to theexamples, figures and tables described below.

DESCRIPTION OF THE FIGURES

FIG. 1 shows the 29-Si MAS NMR spectrum of the dried layered silicatehaving the structure RUB-39 and obtained according to example 2. TMS wasused as standard. The solid-state NMR spectrum was recorded using aBruker ASX 400 with the use of a conventional 7 mm Bruker sample head.The samples were rotated at room temperature through the magic angle atabout 5 kHz spinning speed. For the quantitative spectrum, the HP DEC(high power decoupled) pulse program was used.

FIG. 2 shows the 1-H NMR spectrum of the dried layered silicate havingthe structure RUB-39 and obtained according to example 2. TMS was usedas a standard. The solid-state NMR spectrum was recorded using a BrukerASX 400 with the use of a conventional 4 mm Bruker sample head. Thesamples were rotated at room temperature through the magic angle atabout 12 kHz spinning speed. For the quantitative spectrum, the singlepulse program was used.

FIG. 3 shows the 29-Si MAS NMR spectrum of the calcined tectosilicatehaving the structure RUB-41 and obtained according to example 3. TMS wasused as a standard. The solid-state NMR spectrum was recorded using aBruker ASX 400 with the use of a conventional 7 mm Bruker sample head.The samples were rotated at room temperature through the magic angle atabout 5 kHz spinning speed. For the quantitative spectrum, the HP DEC(high power decoupled) pulse program was used.

FIG. 4 shows the X-ray diffraction patterns of the dried layeredsilicate having the structure RUB-39 (top) obtained according to example2 and of the calcined tectosilicate having the structure RUB41 (bottom)and obtained according to example 3. The powder X-ray diffractionpatterns were recorded on a Siemens D-5000 with monochromatic Cu Kalpha-1 radiation, a capillary sample holder being used in order toavoid a preferred orientation. The diffraction data were collected usinga position-sensitive detector from Braun, in the range from 8 to 96° (2theta) and with a step width of 0.0678°. Indexing of the powder diagramwas effected using the program Treor90, implemented in powder-X (Treor90is a public domain program which is freely accessible via the URLhttp://www.ch.iucr.org/sincris-top/logiciel/). In the figure, the angle2 theta in ° is shown along the abscissa and the intensities are plottedalong the ordinate.

FIG. 5 shows the IR spectrum of the calcined tectosilicate having thestructure RUB-41 and obtained according to example 3 in the range from1,600 to 500 wave numbers. The wave numbers in the unit cm⁻¹ are shownalong the abscissa and the transmission in % along the ordinate. The IRdiagram was recorded using a Nicolet Magna IR-560.

FIG. 6 shows the IR spectrum of the calcined tectosilicate having thestructure RUB-41 and obtained according to example 3 in the range from 4000 to 490 wave numbers. The wave numbers in the unit cm⁻¹ are shownalong the abscissa and the transmittance in % along the ordinate. The IRdiagram was recorded using a Nicolet Magna IR-560.

FIG. 7 shows the nitrogen adsorption isotherm according to example 4(a).The relative pressure p/p⁰ is plotted along the abscissa and the porevolume in ml/g (STP (standard pressure and temperature)), determinedaccording to DIN 66134 at 77 K, is plotted along the ordinate.

FIGS. 8 a and 8 b show the adsorption isotherms according to example4(b). In each case the absolute pressure p(abs) in mbar is plotted alongthe abscissa and in each case the adsorbed amount of n-butane (▴) andisobutane (♦), respectively, in each case in the unitmg(hydrocarbon)/g(zeolite), is plotted along the ordinate.

FIG. 9 shows the adsorption isotherms according to example 4(c). Theabsolute pressure p(abs) in mbar is plotted along the abscissa and theadsorbed amount of methane (▴) and ethane (▪), respectively, in eachcase in the unit mg(hydrocarbon)/g(zeolite), is plotted along theordinate.

FIG. 10 shows the adsorption isotherms according to example 4(d). Theabsolute pressure p(abs) in mbar is plotted along the abscissa and theadsorbed amount of propene (▪), ethene (●), 1-butene (▴) andtrans-2-butene (♦), respectively, in each case in the unitmg(hydrocarbon)/g(zeolite), is plotted along the ordinate.

FIG. 11 shows the adsorption isotherms according to example 4(e). Theabsolute pressure p(abs) in mbar is plotted along the abscissa and theadsorbed amount of n-butane (▪), 1-butene (▴) or trans-2-butene (●), ineach case in the unit mg(hydrocarbon)/g(zeolite), is plotted along theordinate.

FIG. 12 shows the DTG (differential thermogravimetry) curve for thetransition from the layered silicate RUB-39 from example 2 to thetectosilicate RUB-41 from example 3. The temperature in ° C. is plottedalong the abscissa. The weight loss in %, based on the weight of thestarting material, is shown along the left ordinate, which relates tothe DTG curve. The first exothermic maximum at about 350° C. indicatesthe removal of the dimethyldipropylammonium hydroxide compound, and thesecond maximum at about 550° C. indicates the condensation to give thetectosilicate. The DTG analysis was carried out on a Bähr STA 503 at aheating rate of 10° C./h, the dried RUB-39 being heated from roomtemperature to 600° C. under air. The other curve in the diagramrepresents the DTA (differential thermal analysis) carried outsimultaneously on the same apparatus.

EXAMPLES Example 1 Preparation of Dimethyldipropylammonium Hydroxide

15 ml of dipropylamine in 50 ml of ethanol as a solvent and with KHCO₃as a buffer are reacted with 20 ml of methyl iodide at a temperature offrom 40 to 50° C. in a water bath with stirring. After 2 hours, coolingto room temperature was effected, the product dimethyldipropylammoniumiodide crystallizing out. The solid filtrate was washed in ethanol. Anaqueous solution of the iodide was converted over an Amberlyst anionexchanger into dimethyldipropylammonium hydroxide.

Example 2 Preparation of a Layered Silicate

3 g of amorphous silica (Aerosil®) were mixed with 50 ml of an aqueousdimethyldipropylammonium hydroxide solution having a concentration offrom 0.4 to 1 mol/l and were stirred until a colloidal solution wasobtained. The water content of this solution was adjusted in an oven ata temperature of 70° C. so that a mixture having the compositionSiO₂:0.5 dimethyldipropylammonium hydroxide:˜10 water was obtained. Themixture was then transferred to a Teflon-lined stainless steel autoclaveand heated to a temperature of 150° C. at a rate of 15 r.p.m. for aperiod of 30 days with rotation of the autoclave. The mixture obtainedthereby was then quenched with cold water, a high-viscosity suspensionbeing obtained. The novel layered silicate was obtained therefrom byfiltration, washing of the filter residue with water and drying of thefilter residue at 75° C.

The synthesis product had the reflections shown in table 1 in the X-raydiffraction pattern (Cu K alpha 1). TABLE 1 X-ray diffraction pattern ofthe novel layered silicate having the structure RUB-39 2 Theta IntensityI/Io 8.24345 38624.54690 100 11.20594 6132.75830 16 13.39126 6903.0043918 13.92294 2378.23096 6 14.62231 3522.60547 9 15.60788 2344.57275 615.73948 2880.48438 7 16.51815 2821.19092 7 17.47815 2041.75061 518.33579 3715.56616 10 18.57990 4743.49219 12 18.76494 2132.02979 620.00261 9294.63086 24 20.50116 3292.98145 9 21.21685 2926.98779 822.21572 9723.40625 25 22.51286 4358.26807 11 23.51819 10877.29880 2823.66446 10384.66600 27

Example 3 Preparation of a Tectosilicate

The layered silicate obtained according to example 2 was calcined for aperiod of 12 hours at 520° C. and then for a period of 2 hours at 560°C. A tectosilicate which had the reflections shown in table 2 in theX-ray diffraction pattern (Cu K alpha 1 radiation) was obtained. TABLE 2X-ray diffraction pattern of the novel tectosilicate having thestructure RUB-41 2 Theta Intensity I/Io 10.068214 7238.33 100 11.2383232074.58 28.8 13.142148 626.58 8.6 13.343862 686.61 9.5 15.137157 344.834.8 15.693608 977.83 13.5 16.611176 236.25 3.3 16.768200 512.23 7.119.233236 630.60 8.7 19.514395 1200.12 16.6 19.756468 1764.03 24.420.276875 117.92 1.6 21.006195 90.08 1.2 22.653976 265.87 3.7 23.011641996.08 13.8 23.264645 267.16 3.7 24.154955 203.44 2.8 24.373442 212.812.9 26.250389 926.29 12.8 26.369091 966.76 13.2 26.547802 1292.96 17.926.756287 216.20 3.0 26.942410 486.22 7.1

Example 4 Sorption Measurements on the Tectosilicate From Example 3

(a) Measurement With Nitrogen

A pulverulent, freshly calcined sample of the tectosilicate obtainedaccording to example 3 (about 40 mg) was weighed in and was degassedovernight at 120° C. and a reduced pressure of about 10⁻⁶ MPa. Themeasurement was then effected with nitrogen at 77 K on a volumetricsorption apparatus (Autosorb AS-6, from Quantachrome).

FIG. 7 shows the isotherm obtained. The step-like curve of a type Iadsorption isotherm typical of microporous solids is evident (cf. DIN66135). The evaluation of the data gave an equivalent surface of 510m²/g according to the Langmuir method and a micropore volume of 0.18ml/g according to Dubinin-Radushkevich.

(b) Measurement with N-butane and Isobutane

A pulverulent, freshly calcined sample of the tectosilicate obtainedaccording to example 3 (about 140 mg) was weighed in and was degassedovernight at 120° C. and a reduced pressure of about 10⁻⁶ MPa. Themeasurements with n-butane and isobutene, respectively (purity 99.5%)were effected gravimetrically at 296 K on a microbalance (Sartorius4003) over the pressure range up to 800 mbar (pressure transducer fromMKS Baratron).

FIGS. 8 a and 8 b show the isotherms obtained. It is clearly evidentthat the slimmer molecule, n-butane, is preferentially adsorbed, whereasthe more bulky isobutane is taken up only to a slight extent with acapacity of <0.2% by weight. Thus, separation of n-butane and isobutaneis possible with the aid of the tectosilicate RUB-41.

(c) Measurement with Methane and Ethane

A pulverulent, freshly calcined sample of the tectosilicate obtainedaccording to example 3 (about 140 mg) was weighed in and was degassedovernight at 120° C. and a reduced pressure of about 10⁻⁶ MPa. Themeasurements with methane and ethane (purity 99.5%) were effectedgravimetrically at 296 K on a microbalance (Sartorius 4003) over thepressure range up to 866 mbar (pressure transducer from MKS Baratron).

FIG. 9 shows the isotherms obtained. It is clear therefrom that theseparation of methane and ethane is possible with the aid of thetectosilicate RUB-41.

(d) Measurement with Ethene, Propene, 1-Butene and Trans-2-Butene

A pulverulent, freshly calcined sample of the tectosilicate obtainedaccording to example 3 (about 140 mg) was weighed in and was degassedovernight at 120° C. and a reduced pressure of about 10⁻⁶ MPa. Themeasurements with ethene, propene, 1-butene and trans-butene (purity ineach case 99.5%) were effected gravimetrically at 296 K on amicrobalance (Sartorius 4003) over the pressure range up to 865 mbar(pressure transducer from MKS Baratron).

FIG. 10 shows the isotherms obtained. It is clear therefrom that theseparation of the four compounds is possible with the aid of thetectosilicate RUB-41.

(e) Measurement with N-Butane, 1-Butene and Trans-2-Butene

A pulverulent, freshly calcined sample of the tectosilicate obtainedaccording to example 3 (about 140 mg) was weighed in and was degassedovernight at 120° C. and a reduced pressure of about 10⁻⁶ MPa. Themeasurements with n-butane, 1-butene and trans-2-butene (purity in eachcase 99.5%) were effected gravimetrically at 296 K on a microbalance(Sartorius 4003) over the pressure range up to 857 mbar (pressuretransducer from MKS Baratron).

FIG. 10 shows the isotherms obtained. It is clear therefrom that theseparation of the three compounds is possible with the aid of thetectosilicate RUB-41.

1-28. (canceled)
 29. A process for the preparation of a silicatecontaining at least silicon and oxygen, comprising (1) mixing of silica,or of a silica precursor, or of silica and a silica precursor with anaqueous solution containing at least one R₁R₂R₃R₄N⁺-comprisingtetraalkylammonium compound and at least one base; (2) heating of thecolloidal solution obtained according to (1) to a temperature in therange of from greater than the boiling point of the colloidal solutionunder the chosen pressure to 180° C. at normal pressure to give asuspension containing at least one silicate, wherein R₁ and R₂ aremethyl and both R₃ and R₄ are n-propyl.
 30. The process as claimed inclaim 29, wherein the at least one R₁R₂R₃R₄N⁺-comprisingtetraalkylammonium compound contains a basic anion.
 31. The process asclaimed in claim 30, wherein the basic anion is a hydroxide ion.
 32. Theprocess as claimed in claim 29, wherein the aqueous solution employedaccording to (1) contains dimethyldipropylammonium hydroxide (DMDPAH).33. The process as claimed in claim 29, wherein the colloidal solutionobtained according to (1) contains SiO₂, DMDPAH and water in the weightratios SiO₂:DMDPAH:water of 1:(0.45-0.55):(8-12).
 34. The process asclaimed in claim 29, wherein the colloidal solution obtained accordingto (1) is heated according to (2) at normal pressure to a temperature offrom 100 to 180° C.
 35. The process as claimed in claim 29, wherein thecolloidal solution obtained according to (1) is heated according to (2)for a period of from 12 hours to 30 days.
 36. The process as claimed inclaim 29, wherein amorphous silica is employed according to (1).
 37. Theprocess as claimed in claim 29, additionally comprising (3) separationof the at least one silicate from the suspension obtained according to(2).
 38. The process as claimed in claim 37, additionally comprising (4)washing, or (5) drying, or (4) washing and (5) drying of the silicateobtained according to (3).
 39. The process as claimed in claim 38,wherein the silicate is washed according to (4) with water, or is driedaccording to (5) at a temperature in the range of from room temperatureto 80° C., or is washed according to (4) with water and is driedaccording to (5) at a temperature in the range of from room temperatureto 80° C.
 40. The process as claimed in claim 29, additionallycomprising (6) calcination of the silicate obtained according to (2) togive a tectosilicate.
 41. The process as claimed in claim 29,additionally comprising (3) separation of the at least one silicate fromthe suspension obtained according to (2), (4) washing, (5) drying, and(6) calcination of the silicate obtained according to (5) to give atectosilicate.
 42. The process as claimed in claim 40, wherein thecalcination is effected at a temperature in the range of from 300 to600° C.
 43. A layered silicate obtainable by a process according toclaim
 29. 44. A layered silicate having an X-ray diffraction patterncomprising at least the following reflections: Intensity (%) Diffractionangle 2θ/° [Cu K(alpha 1)] 100 8.0-8.4 11-21 11.0-11.4 13-23 13.2-13.6 5-15 18.0-18.4  7-17 18.4-18.8 19-29 19.9-20.0

wherein 100% relates to the intensity of the maximum peak in the X-raydiffraction pattern.
 45. A tectosilicate obtainable by a processaccording to claim
 40. 46. A tectosilicate having an X-ray diffractionpattern comprising at least the following reflections: Intensity (%)Diffraction angle 2θ/° [Cu K(alpha 1)] 100  9.8-10.2 24-34 11.0-11.4 9-19 15.5-15.9 12-22 19.4-19.6 19-29 19.6-19.8

wherein 100% relates to the intensity of the maximum peak in the X-raydiffraction pattern.
 47. The tectosilicate as claimed in claim 46 havinga thermal stability of at least 600° C.
 48. The tectosilicate as claimedin claim 46, wherein the tectosilicate has 8MR and 10MR channels. 49.The tectosilicate as claimed in claim 48, wherein the 8MR and 10MR poreshave a monomodal pore size distribution.
 50. The tectosilicate asclaimed in claim 49, wherein the pores have a specific surface in therange of from 400 to 600 mg²/g, determined according to DIN
 66135. 51.The tectosilicate as claimed in claim 46, additionally comprising Al, B,Fe, Ti, Sn, Ge, Zr, V, Nb or two or more thereof.
 52. A moldingcomprising at least one tectosilicate according to claim
 46. 53. Aprocess for the preparation of a molding, comprising (I) preparing of amixture containing a tectosilicate according to claim 46 and at leastone binder material; (II) kneading of the mixture; (III) molding of thekneaded mixture to give at least one molding; (IV) drying of the atleast one molding; (V) calcining of the at least one dried molding. 54.Method of employing a tectosilicate according claim 46 or of a moldingcomprising at least one tectosilicate according to claim 46 as amolecular sieve, catalyst, catalyst support or binder thereof, as anadsorbent, pigment, additive in detergents, additive for buildingmaterials, for imparting thixotropic properties to coating pastes andfinishes, as external and internal lubricant, as flameproofing agent,auxiliary agent and filler in paper products, in bactericidal orfungicidal or herbicidal compositions, for ion exchange, for theproduction of ceramics, in polymers, in electrical, optical orelectrooptical components and switching elements or sensors.
 55. Methodof separating at least one alkane and at least one alkene and at leastone alkyne, or at least one alkane and at least one alkene, or at leastone alkane and at least one alkyne, or at least one alkene and at leastone alkyne, or at least one alkane, or at least one alkene, or at leastone alkyne from a gas mixture comprising at least two alkanes, or atleast two alkenes, or at least two alkynes, or at least one alkane andat least one alkene, or at least one alkane and at least one alkyne, orat least one alkene and at least one alkyne, or at least one alkane andat least one alkene and at least one alkyne, in the presence of atectosilicate according claim 46, or of a molding comprising at leastone tectosilicate according to claim
 46. 56. The method as claimed inclaim 55, wherein constitutional isomers and configurational isomers, orconstitutional isomers, or configurational isomers are separated. 57.The method as claimed in claim 55, wherein methane and ethane or ethene,propene and butene, or butane and butene, or n-butane and isobutane, or1-butene and trans-2-butene are separated.
 58. Method of synthesizing asilicate in the presence of a R₁R₂R₃R₄N⁺-comprising tetraalkylammoniumcompound as a structure directing agent, wherein R₁ and R₂ are methyland both R₃ and R₄ are n-propyl.
 59. An apparatus comprising at leastone tectosilicate according to claim 46 or a molding comprising at leastone tectosilicate according to claim 46, for the separation of at leastone alkane and at least one alkene and at least one alkyne, or of atleast one alkane and at least one alkene, or of at least one alkane andat least one alkyne, or of at least one alkene and at least one alkyne,or of at least one alkane, or of at least one alkene, or of at least onealkyne from a gas mixture comprising at least two alkanes, or at leasttwo alkenes, or at least two alkynes, or at least one alkane and atleast one alkene, or at least one alkane and at least one alkyne, or atleast one alkene and at least one alkyne, or at least one alkane and atleast one alkene and at least one alkyne.